Recovery of glycerine



Oct. 16, 1951 A. E. CRAVER RECOVERY OF GLYCERINE Filed May 19, 1949 ALCOHOLIC CONCENTRATION FERMENTATION SL0, OF GLYCERINE F|LTRAT|ON COUNTERFLOW DIALYSIS OF THE YEAST m SERIES l L ACIDIFICATION OF FILTRATE gg'Tkg J' l l DISTILLATION ION-EXCHANGE OF ALCOHOL REMOVAL OF INORGANIC SALTS Fig- 1 5 a 4 5 1! l4 F PM "IL, JI I 8 l6 8 l7 8 L 2 L 9 E INVENTOR. AUGUSTUS E. ORAVER JZM YM ATTORNEY Patented Oct. 16, 1951 UNITED STATES PATENT OFFICE RECOVERY OF GLYCERINE Application May 19, 1949, ScrialNo. 94,083

3 Claims.

The invention relates to the recovery of glycerine from fermented liquors.

While glycerol solutions of high clarity and free from impurities may be produced by the fermentation of colorless sugar solutions, molasses from cane or beet sugar is a more economical source of sugar for this purpose. However, the fermentation of molasses solutions always results in a fermented liquor which contains a wide variety of impurities and by-products and has a pronounced dark color. The by-products include volatile substances such as alcohol, acetone, acetic acid, and the like, while the impurities comprise pectins. unfermented sugar, cellulose, natural gums and resins, inorganic salts, especially salts of alkaline earth metals and iron and sulphates. The color of the solution obtained by the fermentation of molasses is due in part to organic colloids and in part to the presence of iron. It is apparent that the recovery of a substantially pure and colorless solution of glycerine from such a complex system involves numerous difficulties.

It is the object of the present invention to provide a method for the production of substantially clear and colorless glycerol solutions from fermentation liquors.

It is a specific object of the present invention to provide a process for the recovery of a substantially clear and colorless solution of glycerol from the liquor produced by the fermentation of molasses.

It is a further specific object to remove from fermentation glycerol solutions such inorganic impurities as calcium, iron, and sulphates.

It is another specific object to reduce the color of glycerol solutions produced by fermentation so that the solution is adapted for use as a softening agent for transparent sheeting and in pharmaceuticals.

A further object is to provide a continuous, counter-current dialysis system comprising a plurality of dialyzers in series for recovering the glycerine, in which the flow of either the dialysate or diiTusate or both may be accomplished either by gravity entirely or the flow within any or all of the cells may be augmented by forced circulation using a pump to increase the circulation or agitation within the respective cells while bleeding oil a portion continuously to the next cell in the series. The forced circulation system increases the agitation of the liquid at the membrane surfaces and thereby increases the rate of dialysis.

Further objects of the invention will in Pa t be obvious and will in part appear hereinafter.

According to the present invention there is provided a process for the purification of fermented liquors including the steps of treating a fermented liquor to filter off the yeast,

acidifying the filtrate, distilling off volatile impurities, such as alcohol, acetone, and so on, concentrating by continued evaporation or distillation, thereafter dialyzing under conditions described hereinafter, percipitating iron from the difiusate and removing other inorganic salts from the difiusate by ion exchange, and, when necessary, decolorizing the diffusate by contacting it with an absorbent material. The glycerine solution obtained as the diffusate may then be concentrated, if desired.

Figure 1 is a flow sheet showing the essential steps of the process, and

Figure 2 is a diagrammatic view of a dialyzing system for executing the invention.

The fermented liquor is subjected to the preliminary treatments specified prior to being subjected to the essential purifying and clarifying steps of the present process starting with dialysis. Normally, it will be desirable to evaporate from the liquor the volatile organic substances, such as alcohol, acetone, acetic acid, and the like. This is normally carried out by distillation in copper stills. Since ammonia is frequently produced during such distillation, it is necessary to acidify the fermenting liquor and to maintain it acid during the distillation. Therefore the residue, after distillation may desirably be neutralized with any suitable alkaline compound, such as lime, sodium hydroxide, p0- tassium bicarbonate, and the like and then concentrated until the liquor is concentrated to about 50% of its volume. Such concentration reduces the volume of liquid to be treated by the subsequent purification process. The fermented liquor, after such concentration, is heated to at least C. and preferably to a temperature above 0., and the heated solution is then dialyzed in counterfiow relationship with water heated to at least 50 0., and preferably above 70 C.

Figure 2 shows a system comprising a .plurality of dialyzing cells (three being shown though more, such as five, six or a greater number, or less than three can be used in series). These cells are designated 3, 4, and 5 and each comprises a cylindrical pipe, vessel or shell 6 containing one or more cylindrical dialyzing membranes 1. While a single vessel 6 may contain up to one hundred or two hundred dialyzing membranes uniformly distributed when viewed in section, such as at the intersections of three sets of equidistantly spaced, parallel lines, of which the lines of each set are inclined at a 60 angle to the lines of the other sets, such as shown in 2,411,238 when one membrane is used as shown, it is preferably supported concentrically within the shell 6 by suitable sealing clamps 8 and 9 provided in the end walls or closures of the shell. The diaphragm or membrane 1 thus divides the interior of the shell into two distinct spaces l and l I between which the sole communication isthrough the semi-permeable membrane 1. A conduit [2 supplies the impure solution to be dialyzed to the central space I0 within the membrane 1 of cell 3. A conduit I3 directs the dialysate from cell 3 into the space I!) of cell 4, and a conduit l4 directs the dialysate from cell 4 to the space ID of cell 5. The final dialysate is discharged through conduit I5 to the next step of the process or to any suitable storage vessel. The water which becomes the diffusate is introduced: by conduit I6, into the annular space H. of cell 5, passes through pipe [1' into space ll of cell 4, and then through pipe i=8 into space H of cell 3 The final diffusate is discharged from the system through pipe I9. Each cell is preferably jacketed at 20 with heat insulation or with a hollow jacket into which a heated fluid may be introduced.

For the dialysis membrane there may be employed parchment paper or a hydrophilic pellicle, such, for example, as regenerated cellulose produced from viscose or by the denitration of nitrocellulose, or from cuprammonia solutions of cellulose. In the now preferred embodiment the dialysis membrane is a tube of regenerated cellulose.

If desired, the dialysate may be concentrated by distillation between the dialyzing cells, and preferably just before entering the final cell in the series. The dialysate and/or the diffusate may be filtered, or chemically treated, such as to raise or lower the pH, between dialyzing cells.

By the dialysis the glycerol and other watersoluble substances are separated from the organic colloids. The diflusate thus obtained is next treated to precipitate iron, such as by a water-soluble sufide, e. g. sodium sulfide. Then, other inorganic salts are removed by passing the diffusate over base exchange salts or resins by which they are converted to sodium compounds.

Cations may then be removed by passing the diffusate over cation absorbing resins, and if. desired, the solution can be decolorized with activated carbon, silica gel or other absorbent. Fo example, with activated carbon, the treatment is carried out at a temperature from 40 to 100 C., preferably 80 C., While the solution is slightly acid. The activated carbon removes most of the residual color due to organic substances. The clarified solution thus obtained is filtered to recover the spent carbon. The spent carbon may be reactivated by heating in a conventional manner and then re-used.

The solution thus obtained is substantially free of iron and alkaline earth metal salts and f sulphates. It is characterized by being substantially clear and colorless, depending upon the extent of decolorizing. The glycerine solution thus obtained is sufficiently clear and colorless to be employed as a softening agent for transparent materials such as cellophane, gelatin, casein and papers of all kinds, including glassine paper, leather, cosmetics and pharmaceuticals, and in the manufacture of synthetic resins.

By way of illustration but not by way of limiting the invention, there will be given the following specific example:

A liquor resulting from the fermentation of molasses in an alkaline medium for the production of glycerol is filtered, rendered slightly acid, and the alcohol and acetone distilled off in a copper'still. The residue is thenconcentrated to about 50% of its initial volume and then neutralized with a 10% aqueous solution of potassium bicarbonate. The concentrated liquid is then heated to about 75 C. and passed through the series of cells of the dialyzing system of Fig. 2 in countercurrent to a stream of water heated to a temperature of 75 C. The semi-permeable membranes were of regenerated cellulose and were entirely covered by the liquids. This submergence of the membranes and operation at high temperature prevented bacterial decomposition of the cellulose. Iron was precipitated from the diffusate by introduction of sodium sulfide, and then the diffusate is passed through an ion exchanger containing a synthetic resin ion exchange absorbent, such as Amberlites IR-IOO and IR-4. The Amberlite IR-IOO is used in the hydrogen cycle (hydrochloric acid as the regenerant) whereas IR-4 is used in the potassium cycle (potassium carbonate as the regenerant). The difiusate is run through a column of 113-100 first and then through IR-4. The diffusate is then treated with activated carbon.

By this process, glycerine solutions introduced into the first cell of the dialyzing system and having between 20 and 35% glycerine content by weight are reduced in the first tube (having a length of about 20 to 25 feet and a diameter of about 1 /2 inches mounted within a 3-inch pipe) to about 9 to 15%, in the second tube to about 5 to 10% glycerine and in the third tube to between less than 0.5 and 3%. The water introduced picks up a content of about to 1 /2% glycerine in the first tube, which is increased to about 1% to 3% in the second tube, and. about 4 to 7% in the third tube when the ratio of water fed to glycerine solution fed is between about 2:1 and 6:1. The difiusate may be further concentrated in conventional manner, if desired.

The continuous series dialysis system has a number of eilects, the benefits of which increase in proportion to the number of dialyzing cells in series. Over-all, these effects result in increased linear velocities of dialysate and diffusate, and consequent increase in the rate of dialysis and efliciency of dialysis per unit area of membrane. These effects or actions are:

(a) sweeping of the droplets of glycerine away from the membrane surface on the diffusate side.

(1)) maintaining the more or less insoluble and/or colloidal or semi-colloidal particles in suspension, thereby reducing or eliminating the clogging by these materials in various parts of the apparatus and particularly the deposition of this material on the membrane, thus partially blocking the dialysis.

(0) increasing of the agitation of both the dialysate and diffusate at the membrane surface.

I claim:

1. A process for recovering glycerine from alcoholic fermentation solutions, comprising the steps of filtering the solution to remove yeast, acidifying the filtrate, removing volatile impurities by distillation, concentrating the distilland to 50% of its original volume by continuing the evaporation or distillation, neutralizing the concentrate with aqueous potassium bicarbonate, passing the concentrate through a plurality of dialyzing cells in series in counter-current flow to water, precipitating iron from the diifusate, removing inorganic salts from the difiusate by subjecting it to ion exchange, and thereafter decolorizing the difiusate by contacting it with an absorbent material, such as activated carbon.

2. A process for recovering glycerine from alcoholic fermentation solutions, comprising the steps of filtering the solution to remove yeast, acidifying the filtrate, removing volatile impurities by distillation, concentrating the distilland to 50% of its original volume by continuing the evaporation or distillation, neutralizing the concentrate with aqueous potassium bicarbonate, passing the concentrate through a plurality of dialyzing cells in series in counter-current flow to water While maintainin the concentrate and water at a temperature of at least 50 C. and said dialyzing cells containing tubular dialyzing membranes made of regenerated cellulose completely submerged in the liquids passing there-- through, precipitating iron from the diffusate, removing inorganic salts from the diffusate by subjecting it to ion exchange, and thereafter decolorizing the difiusate by contacting it with an absorbent material, such as activated carbon.

3. A process as defined in claim 2 wherein the ratio of water to concentrate passed through the plurality of dialyzing cells is between 2:1 and 6: 1.

AUGUSTUS E. CRAVER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,344,850 Bassett June 29, 1920 1,357,138 Bassett Oct. 26, 1920 2,381,055 Hoyt Aug. 7, 1945 2,390,779 Cornwell Dec. 11, 1945 2,437,939 Cornwell et al Mar. 16, 1948 

1. A PROCESS FOR RECOVERING GLYCERINE FROM ALCOHOLIC FERMENTATION SOLUTIONS, COMPRISING THE STEPS OF FILTERING THE SOLUTION TO REMOVE YEAST, ACIDIFYING THE FILTRATE, REMOVING VOLATILE IMPURITIES BY DISTILLATION, CONCENTRATING THE DISTILLAND TO 50% OF ITS ORIGINAL VOLUME BY CONTINUING THE EVAPORATION OR DISTILLATION, NEUTRALIZING THE CONCENTRATE WITH AQUEOUS POTASSIUM BICARBONATE, PASSING THE CONCENTRATE THROUGH A PLURALITY OF DIALYZING CELLS IN SERIES IN COUNTER-CURRENT FLOW 